In a hard disk drive, normally a transducer is positioned by a suspension apparatus over a magnetic disk to facilitate reading and writing of information to the disk. The suspension apparatus is commonly coupled to a rotary actuator which can position the transducer in a radial direction across the magnetic disk. As is well known, the transducer itself is commonly attached to a slider which, in turn, is mounted to the head suspension assembly. During normal operation, the slider actually flies over the surface of the disk due to the hydrodynamic pressure generated by the rotation of the disk. For optimum performance, the flying height must be kept uniform to minimize errors in the reading and writing of data to the disk. Because the magnetic disks themselves are often flawed by imperfections, the slider must be able to pitch and roll over the surface of the disk in order to maintain a uniform flying height. If the slider were inhibited from pitching and rolling over the surface of the disk, then the slider would not be able to accommodate the height variations on the disk. If such were the case, errors in the read/write operations would result.
One of the ways that conventional suspension assemblies have achieved pitch and roll motion is by the incorporation of a dimple which contacts both the top surface of the slider and the load arm of the suspension apparatus. The dimple has a rounded contact point about which the slider can pivot in order to accommodate variations in the topography of the disk. The problem with these types of assemblies is that the radial stiffness of the suspension assembly is generally insufficient to resist rapid motions of the actuator. As is well known, the actuator includes an electromagnetic coil which, when energized, causes the head to be moved from one radial position to another (i.e., from one data track to another). What happens is that as the head is moved across the disk, the dimple slides in a lateral direction to a point on a load arm where the transducer is positioned off-track. Obviously, when this occurs, errors in the reading and writing of data often result. This problem of dimple movement resulting from rapid actuator motion is commonly referred to as the "stick-slip" problem.
One approach to the stick-slip problem has been to increase the stiffness of the load beam and flexure elements of the arm assembly. However, this adds considerable mass to the arm assembly resulting in significantly slower seek times.
Another approach described in U.S. Pat. No. 4,868,694 involves increasing the radial stiffness of the arm assembly by means of a completely redesigned flexure for the rotary actuated load arm. Basically, the flexure is designed to have a U-shaped slot which is perpendicular to the longitudinal axis of the load arm. The drawback of this approach, however, is that it requires a complete redesign of the head suspension apparatus. This means that existing disk drives cannot easily be retrofitted.
Thus, there is a need for a simple solution to the stick-slip problem which does not involve a substantial increase in the mass of the arm, or a major redesign of the head suspension assembly. As will be seen, the present invention provides a solution to the stick-slip problem which is easy to implement and can be incorporated into existing disk drive units.